The present invention relates generally to reflex photographic cameras and, more particularly, to a viewfinder and attachment therefor.
Certain photographic film materials are structured to directly record a positive image of any subject properly imaged and exposed thereon. Exemplary of such materials are the film units described in U.S. Pat. No. 3,415,644, entitled "Novel Photographic Products and Processes" and issued to E. H. Land on Dec. 10, 1968. Film units of this type are intended for use within self-processing photographic cameras of the reflex type as indicated above and incorporate all of the materials necessary to produce a positive photographic print immediately following their exposure. While being of a somewhat complex chemical makeup, the film units are physically structured to include a planar photosensitive element in laminar combination with a transparent image-receiving element. Specially packaged processing units are additionally included within the unit.
To image properly through a lens system upon the above-described film units, it is necessary that one or an odd number of specular surfaces be incorporated within the optical path extending from the camera lens to the exposure plane of the film unit. Although the film units are configured to provide a desirably large film format, certain improved photographic camera designs have taken advantage of the requisite specular surface to achieve somewhat compact overall camera structures. To achieve an even more compact structure which is still capable of exposing large format, e.g., snapshot-sized photographic materials, the traditional solution would appear to reside in a folding type camera. While compactness has been achieved with such cameras as folded, once erected, the cameras generally prove bulky, unbalanced, and usually difficult and uncomfortable to operate.
The most common design employs a vertical exposure plane positioned adjacent a vertical rear outer wall of the camera housing, an objective lens extending forwardly of the housing to establish a straight line optical path between the lens and the vertical exposure plane, and a viewing device mounted on the housing adjacent the rear outer wall through which the photographer looks to aim the lens at the scene to be photographed.
In use, the photographer usually holds the camera housing with two hands to aim the lens at a subject since most of the camera's weight is concentrated forwardly of the exposure plane, thereby making it difficult to manipulate the focusing mechanism and shutter release button with one or two free fingers. Framing a subject through the viewing device can be a frustrating experience. Frequently, the user cannot place his eye close enough to the viewfinder because the vertical rear wall of the camera housing is incompatible with his facial contours. More often than not, when he finally positions his eye to look through the viewfinder, either his nose, check, or forehead bears against the camera housing and he finds it uncomfortable to hold the camera in this position for long periods of time such as while waiting for an uncooperative child to assume an attractive pose. Also, the camera housing tends to block visual and oral communication with the subject, resulting in the photographer having to repeatedly raise and lower the camera to communicate with his subject in preparation for making a photographic exposure.
A recent innovation in the design of folding cameras, namely, the incorporation of folded optical paths into the optical system of the erected camera, has to a large extent eliminated the undesirable characteristics of the traditional folding camera. The folded optical path, in which light passing through the objective lens is reflected within the camera to change its direction, has several advantages. First, since it is not necessary to use a straight line optical path between the lens and the exposure plane, the camera designer is free to place the exposure plane in a horizontal rather than a vertical position. Second, physical spacing between the lens and the exposure plane is no longer equivalent to optical spacing since the optical path may be folded back on itself one or more times, resulting in a camera having a much shorter front-to-rear dimension than the traditional folding camera design.
As indicated in U.S. Pat. No. 3,722,389, there has been developed a compact folding camera incorporating a folded optical path and which includes a viewing device for providing an image of a scene or subject to be photographed. The camera is formed by a plurality of interconnected housing sections, including first and second housing sections, which are coupled for movement between folded and extended positions. The viewing device is mounted on the first housing section and comprises first and second optical means, including first and second optical elements, coupled to the first housing section for movement relative thereto and to one another between inoperative and operative positions. In the inoperative position, the first and second optical elements are folded flat against the first housing section for storage and are movable to the operative position in which they extend outwardly from the first housing section, in optical alignment with one another, thus cooperating to provide an image of a scene or subject to be photographed.
The viewing device further includes means which are responsive to relative movement of the first and second housing sections between the folded and extended positions for moving at least one of the first and second optical elements between its inoperative and operative positions.
As is typical, the user of the camera which is the subject of U.S. Pat. No. 3,722,389, aforesaid, must place his eye proximate the exit pupil of the viewfinder in order to properly view, frame and focus the image of a particular subject at the camera's film plane. Normally, a user would expect to have little difficulty properly positioning his eye with respect to the viewfinder exit pupil, especially where the viewfinder axis lies in substantially the same direction that the camera is aimed at the subject. However, in certain photographic cameras such as illustrated in U.S. Pat. No. 3,722,389 and U.S. Pat. No. 3,710,697, a particularly compact camera structure is provided wherein a collapsible viewfinder assembly is employed having an optical axis generally parallel to the axis of the photographic objective lens assembly of the camera with both the viewfinder axis and the objective lens assembly axis forming an acute angle with respect to the base section of the camera and the film plane. In cameras of this type, it has been found to be difficult for certain operators, especially those wearing vision correcting apparatus, to properly locate and orient their eye at the exit pupil of the viewfinder to achieve proper framing and focusing with respect to a particular subject. It is in response to this difficulty that the present invention was developed.